A liquid crystal display (LCD) has been finding use in an expanded variety of applications covering not only a notebook personal computer and a monitor but also a television set (TV) in recent years. In most cases, a light diffusing plate made of an acrylic resin has been used as a light diffusing plate for a direct type backlight which is to be mounted on a TV and which is requested to have particularly high brightness. Recently, however, a polycarbonate resin that is superior to an acrylic resin in thermal resistance and hygroscopicity has been used as a matrix resin for a light diffusing plate, and there has been a growing demand for the polycarbonate resin.
A sheet obtained by an extrusion molding method has been conventionally the mainstream of a light diffusing plate made of a polycarbonate resin. The reason for the foregoing is as follows: the polycarbonate resin has low melt flowability, so, when one tries to produce a large-area display more than 50 cm (20 inches) on a side by an injection molding method, a molded body to be obtained has problems such as a color tone failure due to the thermal deterioration of the polycarbonate resin and insufficient thickness accuracy.
However, a light diffusing plate obtained by the injection molding method can be expected to provide the following merit: a cost for processing the outside shape of the light diffusing plate obtained by the injection molding method can be reduced as compared to that in the case of a light diffusing plate obtained by the extrusion molding method.
By the way, a copolymer composed of α,α′-bis(4-hydroxyphenyl)-m-diisopropylbenzene (hereinafter, may be referred to as bisphenol M) and 2,2-bis(4-hydroxyphenyl)propane (hereinafter, may be referred to as bisphenol A) has been known (see, for example, Patent Document 1). Known applications of the copolymer are an optical lens (see, for example, Patent Documents 2 and 3) and an optical disk substrate (see, for example, Patent Document 4) because the copolymer has low water absorption property and low birefringence. At present, however, no resin material showing excellent light diffusing performance and excellent moldability has been technically established yet.
In addition, a light diffusing resin composition obtained by blending 100 parts by weight of an aromatic polycarbonate resin produced from bisphenol A with specific amounts of an acrylic resin and a light diffusing agent has been known (see, for example, Patent Document 5).
However, when such aromatic polycarbonate resin is molded into a light diffusing plate, the temperature at which the resin is molded must be increased in order that melt flowability sufficient for an increase in size of the plate may be obtained. However, the color tone of a light diffusing plate to be obtained becomes yellowish owing to the thermal deterioration of the polycarbonate resin to be used, so it is hard to obtain a light diffusing plate having satisfactory performance. In view of the foregoing, a resin material a light diffusing plate molded out of which can be additionally increased in size and has excellent light diffusing performance has been requested.    Patent Document 1: JP 63-89539 A    Patent Document 2: JP 2003-192780 A    Patent Document 3: JP 2003-96179 A    Patent Document 4: JP 2002-348367 A    Patent Document 5: JP 2005-298710 A